Disposable injection device

ABSTRACT

An injection device is provided. The device includes a housing having a first end defining a first opening. A plunger is received within the first opening of the housing to move between first and second positions. A cartridge is disposed in the housing and has an interior serving as a reservoir for a drug. A delivery needle is disposed within the housing and is in fluid communication with the reservoir via an interruptible fluid channel. A locking mechanism is disposed in the housing. In the first position of the plunger the delivery needle is enclosed by the plunger and in the second position of the plunger the delivery needle is placed in an injection position and the plunger activates the locking mechanism whereby when the plunger returns to the first position the locking mechanism prevents the needle from being placed in the injection position.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 10/337,413,filed Jan. 7, 2003, now allowed, the entire contents of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a device for delivering atherapeutic preparation into the body of a patient by injection into orthrough the patient's skin. More particularly, the invention relates toan automatic injection device that incorporates a self-emptyingreservoir.

2. Related Art

The conventional method of administration of a drug to a subject is byinjection using a hypodermic syringe. A number of difficultiesassociated with these syringes have led to attempts to derive moreadvantageous drug delivery devices. Syringes are not generally advocatedfor use in self administration by patients because of the dangers ofembolisms arising from the introduction of air bubbles into thebloodstream, incorrect dosing, and the accidental infection of thirdparties after use of the syringe. In any event, syringes cannot be usedby children or by many elderly patients, and the use of syringes is verytraumatic for the large number of people who are needlephobic to agreater or lesser extent.

Various types of automatic injection devices have been developed toallow drug solutions and other liquid therapeutic preparations to beadministered by untrained personnel. In trying to provide improvedinjection devices, a number of inventors have focused on the provisionof a pre-filled syringe or a pre-filled ampoule for use in a syringe, asthese devices can be useful in addressing the problems of incorrectdosage or incorrect filling of syringes. Furthermore, some syringes havebeen provided with expelling means which automatically deliver the drugfrom the syringe body or ampoule, rather than relying on a conventionalsyringe mechanism which can be difficult to manipulate in a smoothuniform fashion with one hand.

Generally, these devices include some type of automatic needle-drivingmechanism (usually of the spring-loaded type) that can be triggered bythe user. Examples of such devices may be found in U.S. Pat. Nos.4,188,950, 4,196,732, 4,258,713, 4,227,528, and 4,378,015 all to StephenC. Wardlaw. Still further examples can be found in U.S. Pat. No.4,214,584 to Smirnov et al., U.S. Pat. Nos. 4,894,054 and 5,527,287,both to Miskinyar, and U.S. Pat. No. 5,616,132, to Newman. In order tostart the flow of the liquid therapeutic preparation when the needle isinjected, the devices disclosed in the aforementioned patents generallyemploy movable ampoules, pistons or other complex arrangements which aresomewhat difficult to manufacture.

Another class of devices includes those which are capable of graduallyinfusing a liquid therapeutic preparation into the skin of a patient. Insome cases, these devices are small enough (both in height and inoverall size) to allow them to be “worn” by an ambulatory patient whilethe liquid therapeutic preparation is being infused into the patient.Examples of devices which fall in to this class include those disclosedin U.S. Pat. Nos. 4,340,048 and 4,753,651, both to Eckenhoff, U.S. Pat.No. 4,734,092, to Miller, U.S. Pat. No. 4,781,688, to Thoma et al., U.S.Pat. No. 4,886,499, to Cirelli et al., U.S. Pat. No. 5,656,032, toKriesel et al. and PCT Publication Nos. WO 95/13838 and WO 97/21457,both to Elan Medical Technologies, Ltd.

Unfortunately, most of the automatic infusion devices disclosed in theprior art are fairly complex in design and, as a result, cannot be madeas small and inexpensive as might be desired. Generally, the complexityof these devices results from three factors. One factor is the need fora pump or other type of discharge mechanism to force the liquidtherapeutic preparation to flow out of the reservoir and into theinjection or infusion needle. Another factor is the need for some typeof valve or flow control mechanism to cause the liquid therapeuticpreparation to begin to flow at the proper time. A third factor, whichapplies to those devices that are designed to inject the infusion needleinto the patient automatically, is the need for a suitable injectionmechanism that can be triggered by the user. The structures required toperform these functions add size and complexity to the infusion device,making it larger than desired and relatively expensive to manufacture.

Accordingly, a need exists for a drug delivery devise that is capable ofdelivering a pre-set dosage of drug to a subject; is suitable for use inself-administration by patients (including young patients and elderlypatients); does not require the patient to consciously insert a needleinto the skin; includes a safety mechanism to prevent re-use of theneedle; and has a simple construction. Further objects and advantages ofthe invention will become apparent from the description given below.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment of the invention, a bolus injection device isprovided. The injection device comprises a housing having a first enddefining a first opening. A plunger is slidably received within thefirst opening of the housing to move between first and second positions.The plunger has a bottom surface adapted to be brought into contact withthe skin of a subject and prongs extending into the shell. In the firstposition, the plunger at least partially extends out of the firstopening. A resilient member biases the plunger into its first position.A cartridge is disposed in the housing and has an interior serving as areservoir for a drug. The cartridge is moveable between first and secondpositions. A delivery needle is disposed within the housing. Thedelivery needle is out of fluid communication with the reservoir whenthe cartridge is in its first position and in fluid communication withthe reservoir when the cartridge is in its second position, wherein theplunger is moved against the force of the resilient member to its secondposition to expose the delivery needle to the skin of the subject and toactuate movement of the cartridge from its first position to its secondposition.

In another embodiment of the invention, an automatic injection device isprovided. The device comprises a shell having a longitudinal axis anddefines first and second openings on opposite sides of the longitudinalaxis. A plunger is slidably received within the first opening of thehousing to move between first and second positions. The plunger has abottom surface adapted to be brought into contact with the skin of asubject and prongs extending into the shell. In the first position, theplunger at least partially extends out of the first opening. A resilientmember biases the plunger to the first position. A cartridge is disposedin the housing and has an interior serving as a reservoir for a drug. Abutton is disposed in the second opening of the shell to be moveablebetween first and second positions. The button is releasably secured tothe shell to be held in its first position. A needle carrier is disposedwithin the shell and is coupled to the button. A delivery needle isdisposed on the needle carrier opposite from the button, wherein in thesecond position of the plunger the legs engage the button to release itfrom the shell and wherein in the first position of the button thedelivery needle is enclosed with the shell in the second position of thebutton the delivery needle is exposed from the shell and is in fluidcommunication with the reservoir.

According to another embodiment of the invention, an injection device isprovided. The injection device comprises a housing having a first enddefining a first opening. A plunger is received within the first openingof the housing to move between first and second positions. A cartridgeis disposed in the housing and has an interior serving as a reservoirfor a drug. A delivery needle is disposed within the housing and is influid communication with the reservoir via an interruptible fluidchannel. A locking mechanism is disposed in the housing. In the firstposition of the plunger the plunger encloses the delivery needle. In thesecond position of the plunger the delivery needle is in an injectionposition and the plunger actuates the locking mechanism whereby when theplunger returns to the first position, the locking mechanism preventsthe needle from again being placed in the injection position.

Further objectives and advantages, as well as the structure and functionof preferred embodiments will become apparent from a consideration ofthe description, drawings, and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of a preferredembodiment of the invention, as illustrated in the accompanying drawingswherein like reference numbers generally indicate identical,functionally similar, and/or structurally similar elements.

FIG. 1 is a perspective view of a delivery device according to anexemplary embodiment of the present invention;

FIG. 2 is an exploded view of the device of FIG. 1;

FIG. 3 is a cross-sectional view of the device of FIG. 1 in its firstposition;

FIG. 4 is a detailed view of a collar according to an exemplaryembodiment of the present invention;

FIG. 5 is a detailed view of a plunger according to an exemplaryembodiment of the present invention;

FIG. 6 is a detailed view of a safety interlock according to anexemplary embodiment of the present invention;

FIG. 7 is a cross-sectional view of the device of FIG. 1 in its secondposition;

FIG. 8 is a detailed view of a safety interlock in its activatedposition according to an exemplary embodiment of the present invention;

FIG. 9 illustrates an indicator according to an exemplary embodiment ofthe present invention; and

FIG. 10 is a cross-sectional view of a device according to anotherexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are discussed in detail below. Indescribing embodiments, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected. All references cited herein areincorporated by reference as if each had been individually incorporated.

A preferred embodiment of the invention is discussed in detail below.While specific exemplary embodiments are discussed, it should beunderstood that this is done for illustration purposes only. A personskilled in the relevant art will recognize that other components andconfigurations can be used without parting from the spirit and scope ofthe invention.

Exemplary embodiments of the present invention provide a drug deliverydevice adapted for automatic infusion of a drug from a pre-filledcartridge. The drug is delivered to a subject from the cartridge by atleast one delivery cannula. The cartridge is disposed in a housing ofthe device. In use, a distal end of the device is pressed against theskin. This action inserts the delivery cannula into the skin whileinitiating a means for expelling the drug from the cartridge. In oneembodiment, a spring forces the drug from the cartridge through thedelivery cannula and into the skin. After the drug has been delivered,an indicator may alert the user that the injection process is complete.A safety mechanism is engaged when the device is lifted from the skin toprevent the future exposure of the delivery cannula. The drug deliverydevice may then be discarded.

FIG. 1 illustrates a perspective view of a drug delivery device 10according to an exemplary embodiment of the present invention. Thedevice includes a housing 12 having a first end 14 defining a firstopening 16 and a second end 18 defining a second opening 20. A plunger22 is received within the first opening 16 of the housing 12. Theplunger 22 has a bottom surface 24 that is adapted to be brought intocontact with the skin of a subject. The bottom surface 24 of the plunger22 is exposed through the first opening 16. The bottom surface 24 of theplunger may be flat and carry a layer of pressure sensitive adhesivethat allows the device to be affixed to the skin of a patient. Thedevice has a longitudinal axis A-A when the plunger 22 is applied to theskin of a subject.

A vial or cartridge 28 is disposed in the housing 12 along thelongitudinal axis A- A. The cartridge 28 has an interior that serves asa reservoir 46 for a drug or other liquid preparation. In the embodimentillustrated, the cartridge 28 is disposed in the second opening 20 ofthe housing 12 and extends out of the housing. Alternatively, thecartridge can be completely contained within the housing. In use of thedevice, the plunger 22 is pressed against the skin of the subject. Thisinserts a delivery needle into the skin of the subject and initiatesdrug flow. As the drug within the cartridge 28 is expelled, thecartridge 28 moves along the longitudinal axis distally into the housing12, indicating completion of the drug delivery process. A cap 30 may beprovided over the second end 18 of the housing 12 to protect thecartridge 28. The cap may be transparent or include a slot through whichthe movement of the cartridge 28 can be observed.

Referring now to FIGS. 2 and 3, the various components comprising anembodiment of the invention are described in more detail. FIG. 2 is anexploded view and FIG. 3 is a cross-section view. A needle carrier 32 isdisposed in the housing 12. The needle carrier 32 is preferably fixed inplace within the housing 12. A bottom 34 of the needle carrier 32 facesthe first end 14 of the housing 12 as shown in FIG. 3. A pedestal 36extends from the bottom 34 towards the second end 18 of the housing 12.A longitudinal bore 38 extends through the pedestal 36. The longitudinalbore 38 is typically located along the longitudinal axis A-A of thedevice and extends from one end of the pedestal 36 to the other. Anannular surface 40 is arranged around the pedestal 36 with a receivingspace defined between the pedestal 36 and the annular surface 40. Theannular surface 40 is adapted to hold the needle carrier 32 in place inthe housing 12.

A delivery needle 42, which may be a micro-needle array, a single needleor other delivery cannula, is coupled to the needle carrier 32 and is influid communication with the longitudinal bore 38. The delivery needle42 is arranged on a needle hub 34 of the needle carrier 32. The needlehub is cylindrical protrusion from the needle carrier 32. The deliveryneedle 42 is adapted to be placed in an injection position in which itcan penetrate the skin of a user. The length of the delivery needle maybe about 0.5 mm to about 5 mm. The delivery needle can be adapted forintradermal, subcutaneous or intramuscular injection can be used. Thedelivery needle typically has lengths of about 0.5 mm-2 mm forintradermal injection, about 2 mm-3 mm for subcutaneous injection, andgreater than about 3 mm for intramuscular injection. The gauge of thedelivery needle is preferably about 30 to about 34 gauge.

A conduit, such as access needle 44, is in fluid communication with thelongitudinal bore 38 at the end 80 of the pedestal 36 opposite from thedelivery needle 42. The access needle 44 may be arranged in thelongitudinal bore 38 such that a fluid path is established between thedelivery needle 42 and the access needle 44. The access needle 44 may bea relatively large gauge needle, for example about 25 gauge.

The access needle 44 also forms a fluid path for the drug from thecartridge 28 to the delivery needle 42. As mentioned above, the drug tobe delivered is stored in reservoir 46 in the cartridge 28. Thecartridge 28 may be cylindrical in shape with its interior defining thereservoir 46. The cartridge 28 has an open end which is sealed by astopper 48. A rim 50 may be provided on the exterior of the cartridge 28around the open end. The cartridge 28 is disposed in the housing 12above the needle carrier 32, towards the second end 18 of the housing12. The cartridge 28 is movable between first and second positions, thefirst position being prior to use of the device and the second positionbeing following use of the device. The positions of the cartridge 28 aredescribed in more detail below.

A collar 52 may be provided to releasably hold the cartridge 28 in itsfirst position. A detailed view of an example of a collar 52 is shown inFIG. 4. The collar 52 is adapted to fit over an exterior of thecartridge 28. The collar 52 preferably snap-fits over the cartridge 28.Here, the collar 52 is generally cylindrically-shaped with an opencenter to receive the cartridge 28. At least one retaining latch 54 isprovided on the collar 52. The latches 54 include a projecting portion56 that is received by a corresponding surface of the housing 12. Thelatches 54 are preferably resilient and are normally biased outward fromthe collar 52 to engage the housing 12, thereby holding the cartridge 28in place. The collar 52 is also provided with a mating surface 58arranged around the periphery of its open center. The mating surface 58rests against the rim 50 of the cartridge 28 to fit the collar 52 inplace around the open end of the cartridge 28. The collar 52 releasablysecures the cartridge 28 to housing 12 via the retaining latches 54. Thecollar 52 and cartridge 28 may be separate elements as described aboveor formed as an integral unit. In the illustrated embodiment, the collaris formed from an injection-molded polymer. However, the collar 52 mayalso be formed as a stamped metal piece with three prongs serving asretaining latches.

A means for expelling the drug from the cartridge 28 is also provided.The means for expelling the drug may include a resilient member, aspring, or gas pressure. In the illustrated embodiment, the means forexpelling comprises a spring 60. The spring 60 is adapted to move thecartridge 28 from its first position to its second position as isdescribed in more detail below. In the illustrated embodiment, thespring 60 has one end that rests against the collar 52 or is otherwisebiased against the cartridge 28 and a second end which rests against thehousing 12. The spring 60 is arranged coaxially around the cartridge 28.In the first position of the cartridge 28, the spring 60 is compressedas shown in FIG. 3. The cartridge 28 is held in the first positionagainst the force of the compressed spring 60 via the retaining latches54. Cap 30 may be provided over the second end 18 of the housing 12 toprotect the cartridge 28 from damage or contamination.

The plunger 22 is slideably received within the first opening of thehousing 12 to move into and out of the housing 12 between first andsecond positions. A detailed view of a plunger 22 according to anexemplary embodiment of the invention is shown in FIG. 5. The plunger 22has a generally cylindrically shaped body that is hollow and open atboth ends. The needle carrier 32 is received within the hollow body suchthat the plunger 22 is disposed between the needle carrier 32 and thehousing 12 as shown in FIG. 3. The bottom surface 24 of the plunger 22is adapted to be brought into contact with the skin of the subject. Atleast one prong 62 extends from the body into the housing 12 towards thesecond end 18 of the housing 12. The needle carrier 32 may be providedwith slots (not shown) to receive the prong 62 and allow for itsmovement. The prong 62 includes a catch 64 and an actuator 68. The catchhas a delimiting surface 66. The delimiting surface 66 interacts withthe housing 12 to define the first position of the plunger 22 and theneedle hub 34 acts as the delimiting surface for proximal movement ofthe plunger 22, as described in more detail below. The actuator 68 isused to initiate the drug delivery process when the plunger isdepressed.

The drug delivery device may also be provided with a locking mechanismto prevent accidental needle sticks or re-use of the needle. The lockingmechanism may be part of a safety interlock 70 that is illustrated inFIG. 6. The locking mechanism includes a safety spring 72. The safetyspring 72 is coupled to a main body 74 of the safety interlock 70. Oneend of the safety spring 72 is attached at an edge of the main body 74and the other end of the safety spring 72 is moveable. The safety spring72 is resilient and has a relaxed position towards the center of themain body 74. A finger 76 is also provided on the main body 74. Thefinger 76 is flexible and extends upward. As shown in FIG. 6, the finger76 can hold the safety spring 72 back from its relaxed position, at theedge of the main body 74. In this position, the plunger is free to moveto its second position.

The safety interlock 70 may also include a resilient member. Theresilient member biases the plunger 22 outward from the housing 12 intoits first position. In the illustrated embodiment, the resilient membercomprises a wave washer segment 78 coupled to the main body 74. The wavewasher segment 78 is biased against the plunger 22. The safety interlock70 is disposed in the housing 12 between the bottom of the plunger 22and the delivery needle 42. A space is provided between the safetyinterlock 70 and the delivery needle 42 as well as between the safetyinterlock 70 and the annular surface of the plunger 22, when the plunger22 is in its first position. Thus the safety interlock 70 is essentiallyfree floating in the housing 12. A positioning boss may be provided onthe plunger 22 to maintain the safety interlock's position. The mainbody 74 of the safety interlock 70 includes an opening through which thedelivery needle 42 can pass.

Before the device is used, both the plunger 22 and the cartridge 28 arein their first positions and the locking mechanism is held back by thefinger 76. FIG. 3 shows the plunger 22 and the cartridge 28 in theirfirst positions. The cartridge 28 in its first position is arrangedabove the needle carrier 32 and partially extends outside of the housing12 through the second opening 20. The spring 60 is compressed andarranged co-axially around the cartridge 28 and the collar 52. One endof the spring 60 rests against a surface of the housing 12 around aperiphery of the second opening 20. The other end of the spring 60 restsagainst the collar 52. The collar 52 holds the cartridge 28 in place inits first position via the retaining latches 54.

The reservoir 46 in the cartridge 28 contains a precisely measureddosage of a drug. The stopper 48 is positioned at the open end of thecartridge 28 to seal the drug therein. The cartridge 28 and needlecarrier 32 are preferably aligned along the longitudinal axis A-A suchthat stopper 48 is arranged above the pedestal 36 when the cartridge 28is in its first position as shown in FIG. 3. Space may be providedbetween the end surface 80 of the pedestal 36 and the stopper 48 or theend surface of the pedestal 36 may rest against the stopper 48. Thestopper 48 may include a central channel for receiving the access needle44. A barrier 84 blocks the channel preventing the access needle 44 fromreaching the drug. The barrier may be inset from the top surface of thestopper 48 as shown in FIG. 3. In the first position of the cartridge 28the access needle 44 is not yet in fluid communication with thereservoir 46. The access needle 44 may be partially inserted into thestopper 48 or the central channel, but does not completely pierce thestopper 48 or barrier.

The plunger 22 at least partially extends from the first opening of thehousing 12 in its first position. The plunger 22 prevents the deliveryneedle 42 from being accessed from outside the housing 12 when in itsfirst position, as mentioned above. The wave washer 78 biases theplunger 22 into its first position. In the first position of the plunger22, delimiting surface 66 contacts a retaining surface 84 of the housing12. The abutment of the delimiting surface 66 and the retaining surface84 acts against the force of the wave washer 78 to prevent furthermovement of the plunger 22 from the housing 12. Lower delimiting surface66 prevents the wave washer 78 from completely expelling the plunger 22from the housing 12. The location where the retaining surface 84 anddelimiting surface 66 contact each other defines the first position ofthe plunger 22. The first position of the plunger 22 and the safetyinterlock 70 are selected such that the wave washer 78 is biased againstthe plunger 22.

The device is ready for use with the plunger 22 and cartridge 28 intheir respective first positions and the locking mechanism retained byfinger 76. In use, the device is pressed against an injection site on auser. Upon the pressure against the skin of the user, the plunger 22acts against the spring force of the wave washer 78 and is depressedinto the housing 12. The prong 62 on the plunger 22 moves proximallyinto the housing 12. The plunger lifts the safety interlock 70 againstthe needle hub 34 as shown in FIG. 7. When the needle hub 70 engages thesafety interlock, the movement of the plunger 22 into the housing 12 isstopped. Also, an end of the plunger 22 may contact the needle carrier32 as it moves distally into the housing 12 and reaches its secondposition. A thickness of the plunger 22, a thickness of the safetyinterlock 70 and the overall length of the needle determine the depththe delivery needle 42 penetrates into the skin.

As the plunger 22 is pressed against the skin of the subject, theplunger 22 lifts the safety interlock 70 against the needle hub 34. Thesafety interlock 70 is compressed against the needle hub 34 and theneedle hub 34 actuates the locking mechanism. In the illustratedembodiment, the finger 76 is depressed by the needle hub 34 and in turnfrees the safety spring 72 to move radially inward. The safety spring istemporarily prevented from completely moving inwardly. The safety spring72 moves over the finger 76 and temporarily rests against the side ofthe needle hub 34 as shown in FIG. 7.

FIG. 7 illustrates the device with the cartridge 28 and the plunger 22in their second positions. When the plunger 22 reaches its secondposition, the delivery needle 42 is in the injection position and isexposed via the opening in bottom surface of the plunger 22. Due to thepressure placed against the device, the delivery needle 42 penetratesthe skin of the user. At about the same time, the actuator 68 on theprong 62 engages the retaining latches 54 on the collar 52 to releasethe cartridge 28 from the housing 12. In the embodiment illustrated, theprong 62 on the plunger 22 moves proximally and the actuator 68 radiallycompresses the retaining latches 54. The latches 54 are thus releasedfrom corresponding surfaces on the housing 12, which allows movement ofthe cartridge 28. The prong 62 is provided with an engagement surface 65on a backside of the prong. Surface 62 engages a mating surface on thehousing 12 to prevent the prong from spreading as it reaches the latches54. The mating surface on the housing keeps the prong 62 pressed inward.

As the user continues to hold the device against the skin, the drug isinjected through the delivery needle 42 due to the pressure createdinside the cartridge 28 by the compression spring 60 reacting againstthe collar 52. The spring 60 acts against the collar 52 to move thecartridge 28 towards the first end 14 of the housing 12. The end surface80 of the pedestal 36 engages the stopper 48. The pedestal 36 is adaptedto be received within the interior of the cartridge 28. Accordingly, theend surface 80 of the pedestal 36 extends transverse to the longitudinalaxis of the device an amount less than the interior diameter of thecartridge 28. The receiving space around the pedestal 36 should be largeenough to accommodate the collar 52, spring 60 and cartridge 28 as thepedestal 36 enters the interior of the cartridge 28.

As the spring 60 moves the cartridge 28, the access needle 44 piercesthe barrier of the stopper 48 and enters into fluid communication withthe reservoir 46 and the interior of the cartridge 28. Once the stopper48 is punctured, the bore in the access needle 44 forms an escape pathfor the drug. The end surface 80 of the pedestal 36 holds the stopper 48in place. Thus, the stopper 48 is prevented from moving along with thecartridge 28 as the cartridge 28 is driven by the spring 60. The stopper48 acts as a piston and creates a pressure inside the cartridge 28. Thispressure forces the drug contained within the cartridge 28 through theaccess needle 44 into the delivery needle 42. The action of thecartridge 28 being driven down over the stopper 48 thus injects the druginto the user. The drug is pumped through the access needle 44 and afluid channel defined by the longitudinal bore 38 to the delivery needle42 as the stopper 48 is pushed up into the reservoir 46 as a result ofthe spring 60 pushing the collar 52 and cartridge 28 towards the firstend 14 of the housing 12. As the drug is emptied from the cartridge 28,the cartridge 28 moves distally into the housing 12. The spring 60 movesthe cartridge 28 into the housing 12 until the collar 52 or cartridge 28is stopped by a surface of the needle carrier 32 or until the stopper 48reaches the closed end of the cartridge 28 as shown in FIG. 7.

Once the injection is complete, the device is lifted from the skin ofthe subject. Without the pressure from the skin, the wave washer 78forces the plunger 22 distally back to its first position. In turn, thesafety interlock 70 and the locking mechanism also move distally awayfrom the delivery needle 42. As the safety spring 72 is free from theneedle hub 34, it moves radially until it is in its relaxed state distalto the needle hub 34 as shown in FIG. 8. In this position, the lockingmechanism blocks the plunger 22 from moving into the housing 12 and theplunger 22 cannot be depressed proximally. Accordingly, when the plunger22 moves from its second position to its first position, the lockingmechanism is activated to prevent the delivery needle 42 from beingexposed and to prevent accidental needle sticks.

In a further embodiment of the present invention, an indicator isprovided to indicate when the injection process is complete. Theindicator may comprise a resilient member 90 arranged on the outside ofthe second end 18 of the housing 12 as shown in FIG. 9. One end of theresilient member 90 is attached to the housing 12. A second end of theresilient member 90 rests against the cartridge 28 when the cartridge 28is in its first position protruding from the second opening 20. Theresilient member 90 has a relaxed position towards the longitudinal axisof the housing 12 and is biased against the cartridge 28. As describedabove, the cartridge 28 moves distally into the housing 12 as the drugis expelled from the cartridge 28. When the injection of the dose iscomplete, the cartridge 28 is completely within the housing 12. Theresilient member 90 is now free to move to its relaxed state towards thelongitudinal axis of the device. A flag portion 92 of the resilientmember 90 moves over the second opening 20 to indicate that the deliveryof the drug dosage is complete. Also, cap 30 for the device may betransparent to allow the user to observe when the injection of the drugis complete.

FIG. 10 illustrates another embodiment of the present invention. In thisembodiment, the injection device includes a shell 96 having alongitudinal axis B-B. The shell 96 defines first and second openings98, 100 that are arranged on opposite sides of the longitudinal axisfrom each other. The plunger 22 is slideably received within the firstopening 98 of the shell 96 to move between first and second positions.The first position of the plunger 22 is similar to that described above.In this embodiment, the plunger 22 moves between its first and secondpositions in a direction perpendicular to the longitudinal axis of thedevice.

A button 102 is disposed in the second opening 100 of the shell 96. Thebutton 102 is moveable between first and second positions. The button102 is releasably secured in its first position to the shell 96. Areleasable latch may be provided on the button to secure it in its firstposition. The needle carrier 32 is disposed within the shell 96 anddefines a fluid channel. The needle carrier 32 is arranged in betweenthe button 102 and the plunger 22. Preferably, the button 102 is coupledto the needle carrier 32. The delivery needle 42 is disposed on theneedle carrier 32 on the side opposite from the button 102 to be influid communication with the fluid channel. Preferably the button 102,needle carrier 32 and delivery needle 42 are formed as an integral unit.The safety interlock 70 is disposed between the delivery needle 42 andthe plunger 22. Access needle 44 is disposed in fluid communication withthe fluid channel.

Cartridge 28 with stopper 48 is disposed along the longitudinal axis ofthe device and is moveable between first and second positions. Collar 52and spring 60 similar to that described above are also disposed in theshell. In this embodiment, the cartridge 28 moves along the longitudinalaxis of the device in a direction perpendicular to the direction ofmovement of the button and the plunger 22. Two springs 60 are providedto move the cartridge 28 from its first position to its second position.The components of this embodiment may be slightly modified from thatdescribed above to accommodate the different shape of the device.

The relationship of the components in their first position is alsosimilar to the first embodiment described above. When the plunger 22,cartridge 28, and button 102 are in their respective first positions,the device is ready for use. In operation of the second embodiment, theuser pushes the device against their skin. An adhesive layer provided onthe bottom surface of the plunger 22 adheres the device to the skin. Bypressing the device against the skin, the plunger 22 is moved againstthe force of the resilient member and moves distally into the shell 96.This action arms the device by releasing the button 102 from the shell96. The button 102 can be released from the shell 96 by an activator onthe plunger 22 similar to that described above. Here, the activatorengages the releasable latches on the button 102 and compress themradially to release the button 102 from the shell 96. This action armsthe device for injection.

Next, the button 102 is depressed by the user to initiate the injectionprocess. When the button 102 is pressed, the button 102, needle carrier32, and delivery needle 42 move distally and press the delivery needle42 into the skin. Nearly simultaneously, the movement of the button 102to its second position releases the latch holding the cartridge 28 tothe shell, allowing the cartridge 28 to be forced against the needlecarrier 32 under the pressure of the spring 60. Additionally, as theneedle hub 34 and needle carrier 32 press against the safety interlock70, the locking mechanism is activated, freeing the safety spring asdescribed above and allowing it to move radially and rest temporarilyagainst the needle hub 34, as described above.

As the drug is delivered into the skin, the cartridge 28 moves along thelongitudinal axis to its second position. Upon completion of thedelivery of the dose, the device is removed from the skin. As describedabove, the plunger 22 moves distally under pressure from the wave washersegment. This allows the locking mechanism to move radially and preventthe plunger 22 from being depressed to again expose the delivery needle42.

Accordingly, a drug delivery device that is capable of delivering apre-set dosage of drug to a subject is provided. The device is suitablefor use in self-administration by patients (including young patients andelderly patients) and does not require the patient to consciously inserta needle into the skin. A safety mechanism is provided to prevent re-useof the needle. The safety mechanism can be modified to accommodatedifferent needle lengths. In the embodiment described above, the heightthe finger 72 extends from the main body can be changed for differentneedle lengths.

The embodiments illustrated and discussed in this specification areintended only to teach those skilled in the art the best way known tothe inventors to make and use the invention. Nothing in thisspecification should be considered as limiting the scope of the presentinvention. All examples presented are representative and non-limiting.The above-described embodiments of the invention may be modified orvaried, without departing from the invention, as appreciated by thoseskilled in the art in light of the above teachings. It is therefore tobe understood that, within the scope of the claims and theirequivalents, the invention may be practiced otherwise than asspecifically described.

1. An automatic injection device, comprising: a shell having alongitudinal axis and defining first and second openings on oppositesides of its longitudinal axis; a plunger being slidably received withinthe first opening of the housing to move between first and secondpositions, the plunger having a bottom surface adapted to be broughtinto contact with the skin of a subject and a prong extending into theshell, in the first position the plunger at least partially extends outof the first opening; a resilient member biasing the plunger to thefirst position; a cartridge disposed in the housing and having aninterior serving as a reservoir for a drug; a button disposed in thesecond opening of the shell to be moveable between first and secondpositions, the button releasably secured to the shell in its firstposition; a needle carrier disposed within the shell and coupled to thebutton; a needle hub coupled to the needle carrier; and a deliveryneedle disposed on the needle hub, wherein in the second position of theplunger the button is released from the shell and wherein in the firstposition of the button the delivery needle is enclosed with the shelland in the second position of the button the delivery needle is exposedfrom the shell and is in fluid communication with the reservoir.
 2. Thedevice of claim 1, further comprising means for expelling the drug fromthe interior of the cartridge and wherein the button in its secondposition actuates the means for expelling.
 3. The device of claim 1,wherein the cartridge is disposed along the longitudinal axis of theshell.
 4. The device of claim 1, wherein the cartridge is moveablebetween first and second positions within the housing and furthercomprising a collar releasably securing the cartridge to the housing inits first position.
 5. The device of claim 2, wherein the means forexpelling comprises a spring biased against the collar.
 6. The device ofclaim 4, wherein the button in its second position engages the collar torelease it from the housing and the spring biases the cartridge to moveto its second position.
 7. The device of claim 4, wherein the collarfurther comprises a resilient latch normally biased against the housingto secure the cartridge in its first position.
 8. The device of claim 1,wherein the housing further comprises a second end defining a secondopening and the cartridge extends at least partially out of the secondopening in its first position and is contained completely within thehousing in its second position.
 9. The device of claim 1, wherein as thedrug is expelled from the reservoir the cartridge moves form its firstposition to its second position.
 10. The device of claim 1, furthercomprising a pressure sensitive adhesive disposed on the bottom surfaceof the plunger.
 11. The device of claim 1, wherein the button, needlecarrier and needle hub are formed as an integral unit.
 12. The device ofclaim 1, wherein the button moving to its second position moves thedelivery needle into an injection position.
 13. An injection device,comprising; a housing having a first end defining a first opening; aplunger received within the first opening of the housing to move betweenfirst and second positions; a cartridge disposed in the housing andhaving an interior serving as a reservoir for a drug; a delivery needledisposed within the housing and in fluid communication with thereservoir via an interruptible fluid channel; and a locking mechanismdisposed in the housing, wherein in the first position of the plungerthe delivery needle is enclosed by the plunger and in the secondposition of the plunger the delivery needle is placed in an injectionposition and the plunger activates the locking mechanism whereby whenthe plunger returns to the first position the locking mechanism preventsthe needle form being placed in the injection position.
 14. The deviceof claim 13, further comprising an interlock including a first resilientmember biasing the plunger to at least partially extend out of the firstopening.
 15. The device of claim 14, wherein the locking mechanismcomprises a second resilient member connected to the interlock, thesecond resilient member having a relaxed position towards a center ofthe first opening.
 16. The device of claim 13, wherein in the injectionposition the delivery needle is exposed via the first opening.
 17. Thedevice of claim 15, further comprising a latch holding the secondresilient member clear of the first opening to enable the deliveryneedle to be placed to the injection position.
 18. The device of claim15, further comprising a needle hub carrying the delivery needle andwherein in the second position of the plunger, the needle hub releasesthe latch and the second resilient member rests against a side of theneedle hub while the delivery needle is in the injection position. 19.The device of claim 15, wherein when the plunger returns to the firstposition, the second resilient member moves towards the center of thefirst opening and prevents the delivery needle form being placed in theinjection position.
 20. The device of claim 13, wherein the plungerfurther comprises a bottom surface adapted to be brought into contactwith the skin of a subject.
 21. The device of claim 13, furthercomprising means for expelling the drug from the reservoir.
 22. Thedevice of claim 21, wherein the means for expelling comprises a spring.23. The device of claim 13, further comprising an indicator forindicating when the injection is complete.
 24. The device of claim 13,further comprising a needle carrier disposed in the housing, thedelivery needle being attached to the needle carrier.
 25. The device ofclaim 24, wherein the needle carrier is fixed in the housing.
 26. Thedevice of claim 24, wherein a portion of the interruptible fluid channelcomprises a longitudinal bore through the needle carrier, the deliveryneedle being disposed at one end of the bore.
 27. The device of claim26, further comprising an access needle disposed at another end of thebore.
 28. A medical device, comprising: a housing having a first enddefining a first opening; a plunger received with in the first openingof the housing to move between first and second positions; a needle foradministering or withdrawing fluids; and a locking mechanism disposed inthe housing, wherein in the first position of the plunger the needle isenclosed by the plunger and in the second position of the plunger theneedle is placed in an exposed position and the plunger activates thelocking mechanism whereby when the plunger returns to the first positionthe locking mechanism prevents the needle from being placed in theexposed position.
 29. The device of claim 28, further comprising aninterlock including a first resilient member biasing the plunger to atleast partially extend out of the first opening.
 30. The device of claim29, wherein the locking mechanism comprises a second resilient memberconnected to the interlock; the second resilient member having a relaxedposition towards a center of the first opening.
 31. The device of claim28, wherein in the exposed position the needle is exposed via the firstopening.
 32. The device of claim 30, further comprising a latch holdingthe second resilient member clear of the first opening to enable theneedle to be placed to the exposed position.